The present disclosure is related to a spark gap for switching high voltage currents for pulsed power applications.
A spark gap generally consists of an arrangement of two conducting electrodes separated by a gap usually filled with a dielectric gas such as air. When a suitable voltage is supplied across the electrodes, an “avalanche” effect occurs where the electric field between the electrodes ionizes some of the dielectric gas between the electrodes. The ionized gas then conducts a small amount of electricity that heats and further ionizes the gas until the ionized gas becomes a good conductor of electricity, drastically reducing its electrical resistance and heating the dielectric gas, creating plasma between the electrodes. Subsequent current flow through the ionized gas can maintain the conductive channel and keeps the gas heated. The electric current flows until the path of ionized gas is broken or the current reduces below a minimum value so the gas cools and stops conducting.
There are several known techniques for quenching an established arc. One method used is to expend the arc out over a series of gaps (connected in series). By connecting the gaps in series, the voltage drop across an individual gap is reduced. Adding additional gaps in series further lowers the voltage differential at each gap. Once voltage differential drops to a point where the arc is no longer self sustaining, the arc breaks without removing the ionized gas.
A second type of quenching uses flowing air (or other dielectric gas) to disrupt the ionized gas between electrodes. This removes the hot ions from between the electrodes and physically disrupts the established arc but does not alter the electric field between the electrodes.
A third type of quenching is magnetically quenching the gap. Placing a strong magnetic field between the electrodes alters the field formed by the high voltage across the electrodes. This breaks the arc without removing the ionized gas.
A fourth type of quenching is to increase the spark gap. For example, a rotary spark gap consisting of a revolving dielectric disk with electrodes spaced about the rim. The disk is mounted and spun between stationary electrodes. As a moving electrode passes between the stationary electrodes, the gap fires (if there is sufficient voltage potential). As the electrode moves away, the spark gap increases, stretching and breaking the arc. The movement of the disk and the electrode(s) can also serve to disrupt the ionized gas path. The rate the moving electrodes pass between the stationary electrodes can control the rate the gap fires.
There are also several techniques to trigger a spark gap. Triggered spark gaps may include electrodes spaced far enough apart that spontaneous breakdown does not occur without initiating energy. By way of example only, initiating energy could be in the form of UV irradiation from a laser or another spark to heat and ionize the gas between the electrodes. Or the initiating energy could be an over-voltage pulse. Another example method is to vary the gas pressure of the dielectric gas to alter the required breakdown voltage for a particular electrode gap. A rotary spark gap is another example of a triggered spark gap.
Spark gaps can be used to control various resonant circuits, for example, Tesla coils, Oudin Coils and Marx generator circuits. In such systems, the spark gap can operate as a switch to discharge a tank circuit capacitance to the resonant circuit.
Spark gaps can also be used to switch high voltages and high currents for certain pulsed power applications, such as pulsed lasers, pulsed radar, rail-guns, fusion and pulsed magnetic field generators.
Spark gaps can also be used to prevent voltage surges from damaging equipment. For example, spark gaps are used in high-voltage switches. Spark gaps can also be used to protect sensitive electrical or electronic equipment from high voltage surges.